This invention relates generally to refrigerator compressors and more particularly to a reciprocating compressor having a low volume inlet.
Energy efficiency is an extremely important factor in the design of refrigeration systems. This is particularly so for household refrigerators having multiple temperature requirements, e.g., fresh food and freezer compartments. The refrigeration cycle traditionally used in household refrigerators utilizes a single evaporator operated at the low freezer temperature. This cycle is not energy efficient because it produces a refrigeration effect which is appropriate for the freezer compartment but lower than need be for the fresh food compartment.
One approach to better energy efficiency has been the development of more efficient refrigeration cycles. For example, U.S. Pat. No. 5,228,308 issued Jul. 20, 1993 to James Day et al discloses a refrigeration cycle which includes at least two evaporators. A first evaporator is connected to receive at least a portion of the refrigerant discharged from the condenser and a second evaporator is connected to receive a portion of the refrigerant discharged from the first evaporator. A flow control unit is connected to receive at least a portion of the refrigerant discharged from each one of the evaporators. The flow control unit is repeatedly operable to alternately connect one of the evaporators in refrigerant flow relationship with the compressor.
As the flow control unit switches the refrigerant flow relationship, the compressor inlet pressure alternates between the pressures of the two evaporators, a difference of about 15-25 psia. During normal operation, the flow control unit typically switches every 10 seconds. Thus, this refrigeration system has been best implemented using a high-side-case rotary compressor having a low volume inlet. Conventional reciprocating compressors do not work as well because they typically have a low-side-case and thus a high volume inlet. When the inlet pressure of a reciprocating compressor switches to a lower level, a large volume of gas is pumped out of the case to bring the case pressure down to the lower level. This introduces large inefficiencies in the process. However, because reciprocating compressors are generally more efficient and less expensive than rotary compressors, they are more attractive for use in household refrigerators in general.
Accordingly, there is a need for a low volume inlet reciprocating compressor suitable for use in a dual evaporator refrigeration cycle.